It has been widely practiced in electronic devices such as mobile phones or the like provided with a connectors for charging and data transfer to adopt a waterproof structure realized by fitting a cover having an O-ring in an opening area of a housing of an electronic device provided with connector in order to prevent malfunction caused by intrusion of water into the connector.
A cover 210 in this waterproof structure is as shown in FIG. 9(a) and includes a cover main body 211 of a rectangular shape in the front view, and a substantially elliptical projection 212 arranged to protrude to an insertion side from the cover main body 211, wherein a recessed groove 213 is formed in the outer periphery of the projection 212. An O-ring 214 is fitted and installed along the recessed groove 213.
A housing of an electronic device is also provided with a bottomed opening 220 of a substantially elliptical cylindrical shape and a hole 222 is formed in a rear wall 221 of the opening 220, as shown in FIG. 9(b). A connector 230 is placed to face the rear side of the opening 220 so that a tip end of the connector is placed in the hole 222. The connector 230 is connected to a circuit board 233 by a shell 231 and a contact terminal 232 thereof.
Then, the cover 210 is fitted in the opening 220 in such a manner that the O-ring 214 is pressed against and brought into contact with an inner circumferential surface 223 of the opening 120 throughout the entire circumference, whereby preventing water from intruding into the inside beyond an area in which the O-ring 214 and the inner circumferential surface 223 are in contact with each other. Note that a similar structure is disclosed in Patent Document 1.